World background texture not showing in render
For Blender Render (internal), and for a flat repeating background (not a wrap-around 360 background) try the following things:


Add a world texture (if you haven't already)


Properties > Texture panel
Click the "World" tab (it's one of the three little buttons at top of texture panel)
Add texture
Type: Image or Movie
Image > (open image file here)






Check influence


Under the "Influence" section of the world texture I had to check "Horizon" before the world background would render

Check mapping


Mapping > Size
Increase X, Y, and Z values to make background (starfield, in this case) smaller and repeat more often






Sky shading (instead of transparent)


Properties > Render > Shading > Alpha: [Sky]